Standard logging operations have typically involved use of a logging tool which is lowered into the well on a wire including an electrically conductive cable which establishes electronic communication between the logging tool and the surface. Since gravity is the sole means by which the logging tool passes downwardly through the well, standard wireline logging procedures are impracticable for highly deviated and horizontal wells.
In recent years, coiled tubing has been used to effect well logging with the well logging tool attached to the end of the coiled tubing and the necessary wireline cable passing through the inner bore of the coiled tubing. Since the coiled tubing is substantially rigid, the logging tool can be pushed on the coiled tubing laterally outward through highly deviated and horizontal wells. An additional advantage is also available when coiled tubing is used. The internal flow passage of the coiled tubing allows normal coiled tubing operations to be performed either simultaneously with the well logging or, at least, within the same "trip" into the well. Thus, hydraulic packers may be set and released, fluids my be spotted into the well, etc.
The use of logging tools with coiled tubing is not without some difficulty, however. Over the long length of tubing, there is substantial stretch and stretch cycling of both the coiled tubing and the electrical cable passing therethrough. While such stretching is normal and expected with the coiled tubing, the stretching of electrical cable can result in a separation and disconnection of the cable from the logging tool.
In the past, to overcome the problems of cable separation, it has been common to employ an end clamp to secure the lower end of the cable within the logging tool. The clamp generally comprises a split disc transverse to the fluid flow passage which clampingly engages the outer sheath of the cable. In order to maintain the flow passage through such a clamp, the clamp commonly includes a number of holes or slots passing therethrough which allow fluid communication past the clamp. Obviously, however, there is a substantial restriction in the flow passage with the use of this type of clamp.